The present invention relates generally to performance of subterranean operations. Specifically, the present invention is directed to improved methods and systems for treating subterranean formations using a sub-surface mixing system.
Hydrocarbons such as oil and natural gas continue to remain valuable commodities. It is therefore desirable to develop methods and systems that can be used to efficiently extract hydrocarbons from a reservoir. One of the operations that may be used to enhance production from a reservoir is hydraulic fracturing where fractures are formed in the formation and propped open using a proppant to stimulate the formation. When performing hydraulic fracturing operations, a fracturing fluid may be introduced into a portion of a subterranean formation penetrated by a well bore at a hydraulic pressure sufficient to create or enhance one or more fractures therein. Such fractures may be formed for instance, when a subterranean formation is stressed or strained. Stimulation and/or treatment of the well bore in this manner may improve the efficiency of hydrocarbon production from a well bore.
One of the materials that may be used to perform hydraulic fracturing operations is Liquefied Petroleum Gas (“LPG”). Specifically, LPG may be mixed with solid particulates (proppants) such as sand (and/or other desirable materials) at the surface and then directed downhole to perform fracturing operations. For instance, in a typical fracturing operation using LPG, sand may be blended with LPG under pressures greater than 100 psig. High pressure pumps may then be used to pressurize (for instance, to pressures greater than 4000 psig) and flow the gelled LPG-slurry at rates greater than 20 bpm.
However, current methods and systems using LPG have several disadvantages. LPG is primarily comprised of propane and as such, exists in a highly combustible, gaseous form under standard atmospheric conditions. Therefore, to be used as a fracturing fluid, LPG must be mobilized through the fracturing equipment under pressure (usually a pressure between 100 psig and 500 psig). As a result, the LPG inherently has a higher operational hazard risk than conventional aqueous fracturing fluid systems. Consequently, engineering designs to prevent leaks and contingency plans to manage realized leaks are critical to the operation. Further, blending and pumping solid particulates (proppant) with LPG greatly amplifies the aforementioned operational risks and increases the engineering challenges faced in order to prevent and manage LPG leaks. It is therefore desirable to develop a method and system that can be used to safely and efficiently utilize LPG in performance of subterranean operations such as fracturing operations.
While embodiments of this disclosure have been depicted and described and are defined by reference to exemplary embodiments, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.